Water flows through a horizontal $180$ pipe bend. The flow cross$-$sectional area is everywhere $0\mathrm{.}009$ m $2.$ The flow velocity everywhere is $15\mathrm{.}0$ m$/$s$.$ The pressure at the section $1$ and section $2$ is $206,820$ N$/$m$2$ and $165,456$ N$/$m$2$ respectively. Calculate the reaction force R exerted on the fluid by the bend. $[$Ans: R $=-7,396$ N$]$